Pendulum sampler



1964 L. T. WELLENIUS ETAL ,1

PENDULUM SAMPLER Filed July 18, 1960 W e m& e w Wa? vi f A 8 w? MHww n n W United States Patent PENDULUM SAMPLER Lennart Tage Wellenius and Nils Helmer Sandberg,

liristineherg, Sweden, assignors to Bolidens Qruvahtiebolag, Skeileftehamn, Sweden, a company of Sweden Filed duly 18, 196i Ser. No. 43,381 Claims priority, application Sweden July 21, 1959 2 laims. (Cl. 73423) The present invention relates to sampling apparatus, more especially to an apparatus for sampling a stream of free-running particles, for instance a running stream of pulp in ore-dressing.

An object of the invention is to provide a sampling means arranged to be moved along a pendulum path through a stream of the material to be sampled and which used either alone or in combination with a conventional sampler is adapted to give a sample of a proper assay quantity. Thus, swift sample preparation is obtained which is of great importance in for instance sampling for plant supervision. The apparatus can be made fully automatic, thus rendering the expensive hand sampling superfluous.

In ore-dressing plants all over the world the pulp is sampled either by hand directly into a bucket or automatically, for instance through a slot into a scoop which is passed horizontally through a stream of the pulp to be sampled, the portion of the liquid stream passing through the slot being collected in a bucket. The frequency of sampling, i.e. how often and how many times during the sampling operation the slot must be swept through the stream, is calculated according to the accuracy desired. The velocity of the slot, which must be constant, is dependent on the velocity of the material stream to be sampled and the slot width is dependent amongst other things upon the particle size.

In hand sampling and in automatic sampling the assay quantities will be too large and therefore a splitting must be eiiected up to 50 to 100 times. The large samples then must be dried, subdivided into splinters and the like, put into bags, screened and so on. This operation requires a good deal of labour, is time-consuming and usually yields relatively large errors which are great disadvantages in plant supervision. In sampling it is therefore desired to provide for an automatic splitting to an appropriate assay quantity.

The inventors have now found that all the above draw backs may be overcome by fixing a sample container on to a pendulum which is swung across the stream of material to be sampled. The pendulum has a constant period of oscillation and in practice is sufficiently heavy not to be influenced by the stream of material to be sampled through which it is passed. During the short time rcquired to pass across the stream of material the pendulum therefore has a constant velocity which is necessary for an accurate sampling, especially in the case of small samples. Any desired rate of splitting may be obtained, partly by providing the sampling scoop with a slot of variable width and partly by varying the deviation of the pendulum, i.e. the velocity of its oscillatory movement.

The most essential advantage of the invention lies in the fact that the sample may be collected in an appropriate quantity directly into a beaker in which it is then to be dried, thus avoiding dilution in transferring the sample etc. if the pendulum is provided with two slots of different widths and two beakers it is for instance possible to collect a 24 hours sample as well as a short-period sample for rapid testin The sampling time may be further reduced by forming the bottom of the beaker as a detachable filter and separating the principal part of the liquid already during are course of sampling.

In some cases it is convenient to combine the pendulum "ice with some type of primary sampler adapted to start the oscillation. Due to the time required for the sample stream to pass through the tubing through which it is supplied to the sampling pendulum the latter will have attained the maximum and, hence, a constant velocity, the simple transmission thus providing the best possible coordination of a primary sampler and a splitting sampler. Splitting samplers of types other than an oscillatory scoop also are contemplated such as a rotary type of splitting sampler. This type of sampler however, requires 21 separate motor, which involves a disadvantagee.

The invention will be further described with reference to the accompanying drawing, which is a perspective view of a pendulum sampler according to the present invention.

The sampler shown in the figure comprises a tin-box 1 having a rear wall 2, a front wall or panel 3, side-walls 4, 5 and bottom and top plates 7 and 6, respectively. The top plate 6 has a vertically extending tube 8 for continuous supply of the material to be sampled. The tin-box l at its bottom plate 7 has a discharge opening 9 for drawing-oil the waste material of the sampling operation. Inside the closed tin-box a sampling scoop 16 is fixed to an arm 11 and has imparted to it a swivel motion in a horizontal plane by a driving mechanism 12 secured to the top plate 6 of the box 1, said driving mechanism (not shown in detail) essentially comprising an asynchronous motor and a gear box. The sampling scoop lb the top of which is in the shape of a narrow slot 13 tapers downwards and ends in a tubular part inserted into a flexible rubber tubing 14, the lower part of which is threaded on to a rigid elbow tube 15 passing through an opening in the front panel 3 of the tin-box 1 and fastened to the outside of said front panel 3 by means of a flange 16.

Outside the front panel 3 of the tin-box 1 a splitting pendulum 17 is suspended and is journalled in a bearing 18 threaded on to a stud 19 secured to the front panel 3 of the box 1. At the upper part extending over the stud 19 the pendulum 17 is provided with a lever 2% the upper part 21 of which extends a little above the lower edge of the arm 11. Secured to the lower part of the pendulum i7 is a box-like container 22 which, on the side facing the front panel 3 of the tin-box l, is provided with one or more sampling chutes 23, 24 arranged below the outlet 15 of the tubing 14 when the pendulum 17 is in its lowermost position. The upper ends of said samling chutes 23, 24 are shaped as narrow slots 25, 2-6 the long dimensions of which are at right angles to the swingpath of the pendulum 17. Each of the chutes 23, 24 discharges into its collecting containers, nreferably a beaker or cylinder 27 and 23, respectively. Said beakers rest on the container bottom 29 which is fastened to the container by means of a clamping device or clips 39, thus providing a means for easily detaching and re-fastening the bottom for exchange of collecting conta ners.

The apparatus is operated in the following manner:

The arm 11 of the primary sampler is imparted, for instance by an impulse from a time switch or the lih a swinging movement in one or the other direction (to the left in the position shown in the figure), the arm 11 during its movement engaging the extension 21 of the pendulum 17 which is moved towards its outermost position. Simultaneously the sampling scoop It) is passed at a constant rate across the free-falling stream of material ernerging from inlet 8 and a small quantity of the stream is diverted into the scoop it). Before the cut has reached the outlet 15, the pendulum 17 through the arm 11 has been moved to its outermost position, the extension Zl disengaging from the arm 11. The pendulum 17 now is freely oscillating and operating as a secondary sampler or cutter of the primary sample. Since the oscillation can be regarded to be practically undarnped 3 the slots 25, 26 are passing the tube end 15 at a constant velocity. Theoretically it is therefore of no account if the quantity of the sample discharged from the tubing 15 varies in rate and flow area, nor if the proportion of solid and liquid phases varies.

As will be seen from the foregoing description, the scoop may collect a quantity of, for instance, 1 to 10 kgs. and the primary sample has to be split down to to of its original volume. When the scoop is moved from one extreme rest position to the other at a constant rate, it collects, say, 1 liter from the free-fmling stream. The pendulum 17, having been caused to oscillate freely by the engagement of arm 11 with extension 21, oscillates until the material gathered by the scoop is completely exhausted and then continues to oscillate until it comes to rest. The arm 11 is not actuated until the pendulum has-therefore come to rest. As a matter of fact, the interval between each actuation of the arm 11 is so long that a considerable time, e.g. 5 minutes to 4 hour, may have elapsed between each stroke, whereas the pendulum comes to rest after, for instance, 1 minute. It should be observed that the time required for the scoop 10 to be completely exhausted is considerably less, for instance 10 to 20 seconds.

By experiments it has also been found that the primary sample and the split sample have identical properties. The splitting rate of the pendulum is so large that the frequency of the primary sampler can be increased and the slot of its scoop broadened. The samples then will become more accurate which is a further important advantage of the present invention.

In general, the following equations are applicable:

1 .b. Primary sampler O. v

An accurate sample requires a high value of n, generally 21:20. To obtain a low value of q, the slots Width 17 should be small, for practical reasons (clogging), however, not below 4 mms. Normally, Q'is to 80 metric tons' per hour (such as deriving from washing plants), whereas v may be of the order of 150 mrns. per sec. at an rpm. of the motor of 2900. Then it will be found that q amounts to 1 to 10 kgs. which is 10 to 100 times too much. A sample weight of approximately 0.1 kg. is desired, so that the primary sample must be split down to to i of its original volume.

proportionprimary sample to pendulum sample 1, usually 50 to 100) T=time interval between two splitting strokes of the pendulum insec. V v =the horizontal component of the velocity of the slot opening (25 or 26) of the pendulum when passing the the tube outlet (in mms.) b =the width of the slot opening (25 or 26) in mms.

g=acceleration due to gravity in m./sec.

' R =turning radius of the slot opening 25 or 26 in metres R =the radius of the center of gravity of the pendulum in metres I a :th6 maximum deviation angle of the pendulum .,ot=the deviation angleiof the slot opening during the splitting operation The foregoing equations with fair accuracy may be approximated to the following practical equation:

max. 4

As an example, for R =0.5 metre, a =15 and b rnms, there is obtained a less spacious pendulum half the arc element of which is 0.13 metre and \=94, i.e. a fully sufiicient splitting capacity.

With respect to the foregoing it has been found suitable to choose the dimensions of the pendulum so that its length R is 0.3 to 1.0 metre, the angle of deflection u =10 to 30 and the slot width [1 54 mms.

In the foregoing embodiment the pendulum is imparted its initial movement from a conventional primary sampler. Naturally, the pendulum may also be used in sampling in only one step, the initial movement being imparted through mechanical, electrical or hydromechanical means and the entirety of the material stream being sampled by means of the pendulum slots. Instead of operating with one horizontally and one vertically moving sampler it is according to the present invention also possible to use two sampling pendules, wherein the sample cut by means of the first pendulum is continuously passed to a subsequent pendulum sampler which is as a principle arranged in the same manner as hereinabove described.

An apparatus according to the present invention enables automatic splitting at this degree with maintained accuracy. Its use is obviously not restricted to the specific example relating to ground dressed products. Ex amples of other suitable applications are sampling of fibre suspensions in the wood pulping industry, liquid dispersions of raw materials in the Portland cement industry, dry comminuted or pulverulent materials, grain, etc.

Having now described the invention, what we claim as new and desire to secure by Letters Patent, is:

1. An apparatus for obtaining'a divided sample from a free-falling stream comprising a primary sampler having a sampling head with a narrow slotted top adapted to pass across the stream to receive an initial sample therefrom, a horizontally pivoted rigid support arm carrying a said sampling head and adapted to swing said sampling head across said free-falling stream from one extreme rest position to another extreme rest position outside the path of said free-falling stream, a secondary sampler comport carried by the lower end of said pendulum, a pair of sample containers carried by said support, a pair of secondary sampling heads carried by said support and hav-, ing chutes leading to the respective sample containers, a

tube having an outlet discharging the primary sample collected in said sampling head of the primary sampler, said secondary sampling heads having narrow slotted tops which, during the free oscillations of said pendulum, are

adapted to pass repeatedly across the outlet of said tube, means operative upon periodical signals to move said rigid support arm from one extreme rest position to the other at a constant rate engaging the extension of the pendulum and moving said pendulum until the extension thereof slips under the arm thus permitting the pendulum to perform free oscillations While cutting fractions of the sam ple collected in said sampling head until exhaustion thereof,

2. Apparatus according to claim 1, wherein the slotted tops of said secondary sampling heads are of different Widths for taking samples over difierent time periods.

References Cited in the file of this patent UNITED STATES PATENTS Dodd Feb. 18, 1902 Badger Apr. 21, 1903 McCone Feb. 15, 1910 Lien May 24, 1932 Held June 10, 1947 Houston et al. ec. 20, 1955 

1. AN APPARATUS FOR OBTAINING A DIVIDED SAMPLE FROM A FREE-FALLING STREAM COMPRISING A PRIMARY SAMPLER HAVING A SAMPLING HEAD WITH A NARROW SLOTTED TOP ADAPTED TO PASS ACROSS THE STREAM TO RECEIVE AN INITIAL SAMPLE THEREFROM, A HORIZONTALLY PIVOTED RIGID SUPPORT ARM CARRYING SAID SAMPLING HEAD AND ADAPTED TO SWING SAID SAMPLING HEAD ACROSS SAID FREE-FALLING STREAM FROM ONE EXTREME REST POSITION TO ANOTHER EXTREME REST POSITION OUTSIDE THE PATH OF SAID FREE-FALLING STREAM, A SECONDARY SAMPLER COMPRISING A FREELY OSCILLATING PENDULUM HAVING AN UPPER EXTENSION WHICH, WHEN IN REST, PROJECTS INTO THE PATH OF SAID MOVING RIGID SUPPORT ARM FOR ACTUATION THEREBY, A SUPPORT CARRIED BY THE LOWER END OF SAID PENDULUM, A PAIR OF SAMPLE CONTAINERS CARRIED BY SAID SUPPORT, A PAIR OF SECONDARY SAMPLINGS HEADS CARRIED BY SAID SUPPORT AND HAVING CHUTES LEADING TO THE RESPECTIVE SAMPLE CONTAINERS, A TUBE HAVING AN OUTLET DISCHARGING THE PRIMARY SAMPLE COLLECTED IN SAID SAMPLING HEAD OF THE PRIMARY SAMPLER, SAID SECONDARY SAMPLING HEADS HAVING NARROW SLOTTED TOPS WHICH, DURING THE FREE OSCILLATIONS OF SAID PENDULUM, ARE ADAPTED TO PASS REPEATEDLY ACROSS THE OUTLET OF SAID TUBE, MEANS OPERATIVE UPON PERIODICAL SIGNALS TO MOVE SAID RIGID SUPPORT ARM FROM ONE EXTREME REST POSITION TO THE OTHER AT A CONSTANT RATE ENGAGING THE EXTENSION OF THE PENDULUM AND MOVING SAID PENDULUM UNTIL THE EXTENSION THEREOF SLIPS UNDER THE ARM THUS PERMITTING THE PENDULUM TO PERFORM FREE OSCILLATIONS WHILE CUTTING FRACTIONS OF THE SAMPLE COLLECTED IN SAID SAMPLING HEAD UNTIL EXHAUSTION THEREOF. 